1. Field of the Invention
This invention relates to a coupling device of a charging connector assembly for an electric car and more particularly to a coupling device which can be operated under a relatively small force.
2. Statement of the Prior Art
An electric car or automobile will be put to practical use in a near future. At that time, it will be impossible to avoid a problem of charging a battery in the electric car. In particular, a charging connector assembly will be one of important problems to be discussed. The charging connector assembly comprises a car connector connected to a battery in the electric car and a charger connector connected to a charger through a cable.
However, it is necessary to apply a large force to the charging connector in order to positively interconnect terminals in each connector. If a substantial load is caused due to a friction resistance between the connectors during coupling, this may be mistaken for complete coupling. In the case of conducting a charging current through the assembly in the incomplete coupling state, the terminals will generate heat or sparks therebetween when both connectors are displaced.
It is also desired to start conducting after both connectors of the assembly have been completely coupled.
One of the problems in the charging connector assembly is to start a charging operation in the incomplete coupling state of the connectors. If this is done, an abnormal heat may be caused in the assembly, oxidation due to sparks may be caused on the terminals in the assembly, or the assembly will give an operator any electrical shock.
There is a conventional charging connector in which one connector is provided on an outer periphery of an end with a male thread and the other connector is provided on an outer periphery with a rotatable ring which has a female thread adapted to be engaged with the male thread.
The connectors are electrically interconnected by opposing the connectors with each other and rotating the rotatable ring so as to mate the male and female threads. The connectors are electrically disconnected from each other by turning the rotatable ring in a reverse direction.
In the conventional connector assembly mentioned above, the male and female threads are mated with each other by rotation of the rotatable ring to couple both connectors. However, coupling of thread engagement can be easily released.
In comparison with the car connector secured to the car, the charger connector is connected to the charger through the cable.
The charging connector assembly is a relatively large size since a charging current is high and terminals become a large size in compliance with the high current. Since the charger connector is connected to an end of the long cable, a total weight of the connector and cable will be a high amount. Accordingly, it is necessary to make handling of the charger connector easy before hand.
Both connectors must be locked to prevent the charger connector from falling off from the car connector after being coupled. However, since the operator must continuously maintain a coupling force before locking operation has been finished, the operator will be tired. If the operator releases one's hold from the connector assembly in the incomplete coupling state, the charger connector will fall down and be broken. Particularly, such accident will happen in view of the weight of the charger connector.
A coupling device of a charging connector assembly for an electric car must maintain a car connector and a charger connector in a coupling state during charging and release the connectors from coupling after finishing of charging. A coupling device having a lock piece is known which engages with, for example, the charger connector by rotation to maintain the coupling state of both connectors.
However, in the case of using such coupling device, the operator must hold the charger connector by one hand and handle the lock piece by the other hand. Such handling will be troublesome for the operator. Further, the operator must handle the lock piece again to release the connectors after charging has finished.
In a real charging operation, the operator holds the charger connector and pushes it onto the car connector. If, in this case, insulation in the charger connector should deteriorate to leak out the charging current, a serious accident will happen.
As described above, it is necessary to take into consideration of coupling operation and safety of charging in designing of the charging connector assembly. For example, a mechanism for aiding a coupling force or a switch mechanism which permits conduction after confirming a safe condition is required. Particularly, it will be preferable to form the charger connector into a gun type shape in order to facilitate the coupling operation. In addition to the gun type shape, a lever may be provided to enhance handling of the coupling device.
However, even if the lever is provided on the device, it may be actuated before completing a condition of coupling aid and safety unless the lever is constrained from operating under an unsafe condition.